Power supply, light emission control device and display device
First Claim
1. A power supply comprising:
- a charge pump circuit to periodically turn on and off a plurality of charge-transfer switches according to a clock signal, to thereby charge and discharge a charge storage capacitor and thereby produce a desired output voltage from an input voltage to supply the thus produced output voltage to a load, wherein, as the current flowing through the load is detected by an output current detection circuit, a current commensurate with the output current is detected;
a transistor to extract the current commensurate with the output current;
a sense resistor through which the current commensurate with the output current flows; and
a comparator whose output level varies according to a potential difference across the sense resistor,wherein a frequency of the clock signal is varied according to the current flowing through the load.
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Accused Products
Abstract
The power supply of the present invention is composed of: a charge pump circuit (54) that periodically turns on and off a plurality of charge-transfer switches (Q1 to Q4) according to clock signals (c1 and c2), thereby charges and discharges a charge storage capacitor (C1) and thus produces the desired output voltage (Vo) from an input voltage (Vi) to supply it to a load (LED); an output current detection circuit 57 for detecting an output current Io (a reference current (Im) thereof in FIG. 1) to the load; and means (a frequency conversion circuit 52 in FIG. 1) that varies the frequency of the clock signals c1 and c2 based on the result of the detection of the output current Io. With this configuration, it is possible to achieve high electric power efficiency irrespective of the magnitude of a load.
10 Citations
10 Claims
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1. A power supply comprising:
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a charge pump circuit to periodically turn on and off a plurality of charge-transfer switches according to a clock signal, to thereby charge and discharge a charge storage capacitor and thereby produce a desired output voltage from an input voltage to supply the thus produced output voltage to a load, wherein, as the current flowing through the load is detected by an output current detection circuit, a current commensurate with the output current is detected; a transistor to extract the current commensurate with the output current; a sense resistor through which the current commensurate with the output current flows; and a comparator whose output level varies according to a potential difference across the sense resistor, wherein a frequency of the clock signal is varied according to the current flowing through the load. - View Dependent Claims (2, 3, 7, 8, 9, 10)
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4. A power supply comprising:
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a charge pump circuit to periodically turn on and off a plurality of charge-transfer switches according to a clock signal, to thereby charge and discharge a charge storage capacitor and thereby produce a desired output voltage from an input voltage to supply the thus produced output voltage to a load, wherein, as current flowing through the load is detected by an output current detection circuit, a current commensurate with the output current is detected, and wherein the current flowing through the load is monitored through monitoring of a predetermined control signal used to control a drive current for the load; a drive current generating circuit to generate the drive current for the load; and a digital-to-analog converter to generate an analog control signal suitable for control of the drive current generating circuit from a digital control signal for setting the drive current supplied to the load, wherein the control signal used for monitoring the current flowing through the load is the digital control signal, and wherein a frequency of the clock signal is varied according to the current flowing through the load. - View Dependent Claims (5, 6)
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Specification